Part 238

V.—For a temporary frosting, dip a piece of flat marble into glass cutter’s sharp sand, moistened with water; rub over the glass, dipping frequently in sand and water. If the frosting is required very fine, finish off with emery and water. Mix together a strong, hot solution of Epsom salt and a clear solution of gum arabic; apply warm. Or use a strong solution of sodium sulphate, warm, and when cool, wash with gum water. Or daub the glass with a lump of glazier’s putty, carefully and uniformly, until the surface is equally covered. This is an excellent imitation of ground glass, and is not disturbed by rain or damp.

VI.—This imitates ground glass:

Sandarac 2 1⁠/⁠2 ounces Mastic 1⁠/⁠2 ounce Ether 24 ounces Benzine 16 to 18 ounces

VII.—Take white lead ground in a mixture of 3⁠/⁠4 varnish and 1⁠/⁠4 oil of turpentine, to which burnt white vitriol and white sugar of lead are added for drier. The paint must be prepared exceedingly thin and applied to the glass evenly, using a broad brush. If the windows require a new coat, the old one is first removed by the use of a strong lye, or else apply a mixture of hydrochloric acid, 2 parts; vitriol, 2 parts; copper sulphate, 1 part; and gum arabic 1 part, by means of a brush. The production of this imitation frosting entails little expense and is of special advantage when a temporary use of the glass is desired.

VIII.—A little Epsom salt (sulphate of magnesia) stirred in beer with a small dose of dextrin and applied on the panes by means of a sponge or a brush permits of obtaining mat panes.

«Hoarfrost Glass.»—The feathery foams traced by frost on the inside of the windows in cold weather may be imitated as follows:

The surface is first ground either by sand-blast or the ordinary method, and is then covered with a sort of varnish. On being dried either in the sun or by artificial heat, the varnish contracts strongly, taking with it the particles of glass to which it adheres; and as the contraction takes places along definite lines, the pattern given by the removal of the particles of glass resembles very closely the branching crystals of frostwork. A single coat gives a small, delicate effect, while a thick film, formed by putting on 2, 3 or more coats, contracts so strongly as to produce a large and bold design. By using colored glass, a pattern in half-tint may be made on the colored ground, and after decorating white glass, the back may be silvered or gilded.

«Engraving, Matting, and Frosting.»—Cover the glass with a layer of wax or of varnish on which the designs are traced with a graver or pen-point; next, hydrofluoric acid is poured on the tracings. This acid is very dangerous to handle, while the following process, though furnishing the same results, does not present this drawback: Take powdered fluoride of lime, 1 part, and sulphuric acid, 2 parts. Make a homogeneous paste, which is spread on the parts reserved for the engraving or frosting. At the end of 3 or 4 hours wash with water to remove the acid, next with alcohol to take off the varnish, or with essence of turpentine if wax has been employed for stopping off.

«To Render Window Panes Opaque.»—I.—Panes may be rendered mat and non-transparent by painting them on one side with a liquid prepared by grinding whiting with potash water-glass solution. After one or two applications, the panes are perfectly opaque, while admitting the light.

II.—Paint the panes with a solution of

Dextrin 200 parts by weight Zinc vitriol 800 parts by weight Bitter salt 300 parts by weight In water 2,000 parts by weight

III.—For deadening panes already set in frames the following is suitable: Dissolve 1 part of wax in 10 parts of oil of turpentine, adding 1 part of varnish and 1 part of siccative. With this mixture coat the panes on the outside and dab, while still wet, with a pad of cotton wadding. If desired small quantities of Paris blue, madder lake, etc., may be added to the wax solution.

IV.—For deadening window panes in factories and workshops: To beeswax dissolved in oil of turpentine, add some dryer and varnish to obtain a quicker drying and hardening. After the window pane has been coated with this mixture on the outside, it is dabbed uniformly with a pad of wadding. The wax may be tinted with glazing colors.

«Frosted Mirrors.»—I.—Cover with a solution of Epsom salts in stale beer; apply with a sponge to the mirror, first wiping it clean and dry. On drying, the Epsom salt crystallizes, giving very handsome frosted effects, but the solution must not be applied on humid days {376} when the glass is liable to be damp, for in that case the effect will be a blurred one. When it is desirable to remove the coating, lukewarm water will serve the purpose without damage to the luster of the mirror.

II.—The following mixture, when applied to a mirror and left to dry, will form in many shapes, all radiating from a focus, this focus forming anywhere on the glass, and when all dry tends to form a most pleasing object to the eye.

Sour ale 4 ounces Magnesium sulphate 1 ounce

Put on the mirror with a small, clean sponge and let dry. It is now ready for the artist, and he may choose his own colors and subject.

«Crystalline Coatings or Frostwork on Glass or Paper.»—Dissolve a small quantity of dextrin (gum arabic and tragacanth are not so suitable) in aqueous salt solution as concentrated as possible, for instance, in sulphate of magnesia (bitter salt), sulphate of zinc or any other readily crystallizing salt; filter the solution through white blotting paper and coat glass panes uniformly thin with the clear filtrate, using a fine, broad badger brush; leave them lying at an ordinary medium temperature about one-quarter hour in a horizontal position.

As the water slowly evaporates during this short time, handsome crystalline patterns, closely resembling frostwork, will develop gradually on the glass panes, which adhere so firmly to the glass or the paper (if well-sized glazed paper had been used) that they will not rub off easily. They can be permanently fixed by a subsequent coat of alcoholic shellac solution.

Especially handsome effects are produced with colored glass panes thus treated, and in the case of reflected light by colored paper.

For testing crystals as regards their optical behavior, among others their behavior to polarized light, it is sufficient to pour a solution of collodion wool (soluble peroxide lime for the preparation of collodion) over the surface of glass with the crystalline designs, and to pull off the dry collodion film carefully. If this is done cautiously it is not difficult to lift the whole crystalline group from the glass plate and to incorporate it with the glass-like, thin collodion film.

«REMOVING WINDOW FROST.»

Here are fourteen methods of preventing frost on windows, arranged in the order of their efficacy: 1, Flame of an alcohol lamp; 2, sulphuric acid; 3, aqua ammonia; 4, glycerine; 5, aqua regia; 6, hydrochloric acid; 7, benzine; 8, hydriodic acid; 9, boric acid; 10, alcohol; 11, nitric acid; 12, cobalt nitrate; 13, infusion of nutgalls; 14, tincture of ferrous sulphate. By the use of an alcohol lamp (which, of course, has to be handled with great care) the results are immediate, and the effect more nearly permanent than by any other methods. The sulphuric acid application is made with a cotton cloth swab, care being taken not to allow any dripping, and so with all other acids. The effect of the aqua ammonia is almost instantaneous, but the window is frosted again in a short time. With the glycerine there are very good results—but slight stains on the window which may be easily removed.

The instructions for glycerine are: Dissolve 2 ounces of glycerine in 1 quart of 62 per cent alcohol containing, to improve the odor, some oil of amber. When the mixture clarifies it is rubbed over the inner surface of the glass. This, it is claimed, not only prevents the formation of frost, but also prevents sweating.

«To Prevent Dimming of Eyeglasses, etc.»—Mix olein-potash soap with about 3 per cent of glycerine and a little oil turpentine. Similar mixtures have also been recommended for polishing physicians’ reflectors, show-windows, etc., to prevent dimming.

«WRITING ON GLASS:»

See also Etching and Inks.

«Composition for Writing on Glass.»—To obtain mat designs on glass, take sodium fluoride, 35 parts; potassium sulphate, 7 parts; zinc chloride, 15 parts; hydrochloric acid, 65 parts; distilled water, 1,000 parts. Dissolve the sodium fluoride and the potassium sulphate in half the water; dissolve the zinc chloride in the remaining water and add the hydrochloric acid. Preserve these two solutions separately. For use, mix a little of each solution and write on the glass with a pen or brush.